1. Field of the Invention
The present invention relates to a non-aqueous electrolyte secondary battery with filling function (hereinafter referred to as a “secondary battery with filling function”), as well as a non-aqueous electrolyte secondary battery (hereinafter referred to as a “corresponding secondary battery”) and a non-aqueous electrolyte filling device (hereinafter referred to as a “filling device”) used therefor, and particularly to a secondary battery with filling function capable of being refilled with a non-aqueous electrolyte in a low humidity environment as well as a corresponding secondary battery and a filling device used therefor.
2. Description of the Background Art
A non-aqueous electrolyte secondary battery such as a lithium ion secondary battery has a high voltage and high energy density and it is superior in reliability such as storage capability and resistance to leakage. Therefore, the non-aqueous electrolyte secondary battery has already been put into practical use as a small-sized power supply in a portable telephone, a notebook personal computer and the like, and medium- or large-scale applications thereof such as automobile applications or power storage applications have also been attempted.
Examples of a positive electrode active material for the lithium ion secondary battery include not only titanium disulfide, vanadium pentoxide and molybdenum trioxide but also various compounds expressed by a general formula LixMO2 (M being one or more type of transition metal), such as lithium cobalt composite oxide, lithium nickel composite oxide and spinel-type lithium manganese oxide.
Examples of a negative electrode active material for the lithium ion secondary battery include not only metal lithium and an alloy containing lithium but also various materials such as carbon materials capable of occluding and releasing lithium. In particular, use of a carbon material as a negative electrode active material is advantageous in that a battery having long cycle life is obtained and high safety is achieved.
In general, an electrolytic solution obtained by dissolving a supporting electrolyte such as LiPF6 or LiBF4 in a mixture-type solvent of a solvent having a high dielectric constant such as ethylene carbonate or propylene carbonate and a low-viscosity solvent such as diethyl carbonate is employed as a non-aqueous electrolyte for the lithium ion secondary battery.
The lithium ion secondary battery so far is of a sealed type and it also has long charge and discharge cycle life. Therefore, if the lithium ion secondary battery is used prescribed number of times and its discharge capacity has significantly lowered, it was determined that the battery life had expired and the battery was disposed of. The lithium ion secondary battery that had been disposed of has been recovered and a material that can be used has been extracted for recycling.
It has been difficult, however, to recycle 100% of materials making up the battery, and it has been demanded to conceive a method of effectively utilizing a battery of which life had expired. In the case of the lithium ion secondary battery for medium- or large-scale applications as described above, life of 10 to 20 years and charge and discharge cycle life of several thousand to several ten thousand cycles may be required.
However, it is difficult to achieve such long life with a conventional battery configuration.
In order to address this, for example, Japanese Patent Laying-Open No. 2001-210309 proposes a lithium ion secondary battery in which an inlet port stopper is provided in a battery container in order to recover discharge capacity by refilling the lithium ion secondary battery of which discharge capacity has lowered due to repeated charge and discharge cycles with a new non-aqueous electrolyte.
The non-aqueous electrolyte, however, should be handled in a low-humidity environment, and for example, it is handled in such facilities as a glove box of which humidity is controlled. Therefore, in general, in refilling a lithium ion secondary battery with a non-aqueous electrolyte, the lithium ion secondary battery had to be moved into the facilities above and an operation has been complicated.
In addition, since a lithium ion secondary battery used for power storage applications or automobile applications has a large size, an operation within such facilities as a glove box or loading the lithium ion secondary battery into the glove box may be difficult. Therefore, it is difficult to fill the medium- or large-sized lithium ion secondary battery with the non-aqueous electrolyte in a low-humidity environment.
Moreover, as compared with a small-sized lithium ion secondary battery used in a portable phone or a personal computer, with regard to a lithium ion secondary battery for power storage or for automobiles having a medium or large size and desired to have longer life, lowering in capacity retention due to exhaustion of a solution is a serious and unignorable problem.